The general election of 1918(in Ireland) was, in Irish republican theory, to fill the 105 seats in Dáil Éireann for the First Dáil. In practice only the Sinn Féin MPs took their seats as Teachtaí Dála in Dublin. This Dáil first assembled on 21 January 1919 and last met on 10 May 1921. Under a resolution passed at its last meeting the First Dáil was dissolved upon the assembly of the Second Dáil, which took place on 16 August 1921.

However the Oireachtas members database regards the First Dáil as having existed 21 January 1919 – 10 May 1921.

The Irish elections, 1921 comprised separate elections in the six counties of Northern Ireland and the twenty-six counties of Southern Ireland. In Irish republican theory, there was one election to fill the 180 seats (52 from Northern Ireland and 128 from Southern Ireland) in the Second Dáil. In practice, only the Sinn Féin MPs took their seats as Teachtaí Dála in Dublin. This Dáil first assembled on 16 August 1921, and last met (at least in the view of the subsequent Irish Free State) on 8 June 1922.

The Second Dáil was not formally dissolved, but following the precedent of 1921, it should perhaps be regarded (from the viewpoint of the Irish Free State) as dissolved upon the assembling of the Third Dáil. The Third Dáil was first summoned to meet on 1 July 1922. It was prorogued on five occasions and eventually met on 9 September 1922.

However the Oireachtas members database regards the Second Dáil as having existed 24 May 1921 – 16 June 1922.

In republican theory, the Second Dáil continued to exist, and no subsequent Dála were legitimate, as they only represented part of Ireland.

1948–61: There was a redistribution of seats under the Electoral (Amendment) Act 1947 (No. 31/1947). The new constituencies were used for the 13th to 16th Dála.

1961–69: There was a redistribution of seats under the Electoral (Amendment) Act 1961 (No. 19/1961). The new constituencies were used for the 17th and 18th Dála.

1969–77: There was a redistribution of seats under the Electoral (Amendment) Act 1969 (No. 3/1969). The new constituencies were used for the 19th and 20th Dála. This was the first redistribution which did not divide constituencies into borough and county seats. To preserve continuity in the tables the seats based upon the cities of Cork and Dublin are treated as if they were borough constituencies and all the other seats are recorded as county ones.

1977–81: There was a redistribution of seats under the Electoral (Amendment) Act 1974 (No. 7/1974). The new constituencies were used for the 21st Dáil.

1981–92: There was a redistribution of seats under the Electoral (Amendment) Act 1980 (No. 17/1980) and the same constituencies and numbers of seats (with minor boundary changes) were re-enacted by the Electoral (Amendment) Act 1983 (No. 36/1983). The new constituencies were used for the 22nd to 24th and 25th to 26th Dála respectively. Constituency names, in Cork and Dublin, ceased to reflect the difference between borough and county constituencies. Some seats combined territory from the Cork or Dublin County Borough and Administrative County areas, although those seats are still treated as borough constituencies for the purpose of the tables.

1992–97: There was a redistribution of seats under the Electoral (Amendment) Act 1990 (No. 36/1990). The new constituencies were used for the 27th Dáil.

1997–2002: There was a redistribution of seats under the Electoral (Amendment) Act 1995 (No. 21/1995). The new constituencies were used for the 28th Dáil.

(1) Constituencies which include all or part of two or more counties are attributed to the first county mentioned in the constituency name or (if none) the predominant county.

(2) Constituency names are based upon those used in the Oireachtas database of former members, except that borough division names in 1918 and 1997 are not placed in brackets. These names are sometimes not identical to those used in electoral legislation, i.e. compass points always follow the county or borough name in the database.

(3) The official designation of borough and county constituencies ended in 1969. After that time constituencies which included more than a small part of the county boroughs of Cork and Dublin are referred to as borough constituencies in this article, to preserve the continuity of the tables.